This involved setting up fake Facebook accounts bearing his name in the hope that those close to him would be lured into making contact or answering private messages, potentially giving away personal details about Stavridis or themselves.

This type of “social engineering” impersonation is an increasingly common web fraud. Nato said it wasn’t clear who was responsible for the spoof Facebook pages, but other security sources pointed the finger at China.

Last year, criminals in China were accused of being behind a similar operation, which was given the codename Night Dragon. This involved hackers impersonating executives at companies in the US, Taiwan and Greece so that they could steal business secrets.

The latest disclosure will add to growing fears in the UK and US about the scale of cyber-espionage being undertaken by China. As well as targeting senior figures in the military, the tactic has been blamed for the wholesale theft of valuable intellectual property from some leading defence companies.